Cartridge-fuse.



AfL. EUSTICE.

CARTRIDGE FUSE'. APPLICATION FILEDJUNE22.1914.

Patented Feb.27,1917.

27 26 J9 J9 2g 25 UNITED sTATEs PATENT oEErcE.

ALFRED L. EUS'IICE, OF CHICAGO,

ILLINOIS, ASSIGNOR T ECONOMY FUSE sa MANU-- FACTURING COMPANY, OFCHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

CARTRIDGE-FUSE.

Specification of Letters Patent.

Patented Feb. 27, 1917.

Application led .Tune 22, 1914. Serial No. 846,474.

-inclosed fuses, used for the protection of electricv circuits, andv isparticularly (although not exclusively) concerned with fuses of theso-called renewable type.

It is one of the objects of my invention to so construct a cartridgefuse that it is unnecessary to employ in said fuse a non-conductingilling material of any kind. Heretofore 1t has been customary to employwithin the casing of the fuse a non-conducting filling material eitherin the form of a powder, such as lime, plaster of Paris, asbestos, or afiller in the form of fibrous material, such as a woven asbestos sleeve,or the like. I have found that in an inclosed fuse having my improvedlink which is hereinafter described, the use of a filling material ofany kind may be avoided by so constructing an inclosed fuse that onblowing the fuse the gases which are generated are restricted in -theirpassage from the casing. The principle which I employ in restricting theescape of the gases is much the same as that employed in the well-knownautomobile mufiiers, Maxim silencers, and other similar devices whichdeaden the noise of an explosion by restricting the path of escape ofthe generated gases.

In the present application my invention is describedV as appliedparticularly to fuses of the so-called knife-blade type, in which theterminals project into the ends of the inclosingfcasing of the fuse.These terminals are suitably alined and centered, and a resilientclosing member is provided to prevent the escape of gases directlythrough the ends of the fuse, the restricted paths for the escapinggases being formed between the screw threads on the ends of the, casingand those in the end caps of the fuse.

A further object of my invention consists in reducing to a minimum theamount of metal which is volatilized on blowing of the fuse, and Iaccomplish this result by prol viding the fuse link (which is preferablyflat) of the cartridge or other inclosed fuse with a'plurality ofrestricted or substantially more quickly melting portions, theserestricted portions preferably being formed by notching the sides of thelink, and thus substantially reducing the cross-sectional area of thelink at these portions. In this manner, on blowing of the link withinthe inclosed fuse the melting and volatilization of the metal occursonly at the restricted portions of the link, and the portions of thelatter between such restricted portions vare instantaneously separatedfrom the balance of the link and are not melted, thus greatly reducingthe amount of gases generated by the blowing of the fuse. I ordinarilyemploy two restricted portions of the link near the ends thereof so thatthe greater portion of the link is caused to drop and separate itselffrom the balance of the link on blowing the fuse. In the case of fusesfor high voltage circuits I preferably increase the number of restrictedportions in the link, thereby correspondingly reducing the voltage ateach restricted portion; for example, if a link is provided with tworestricted portions, and is blown on a circuit of 500 volts, the voltageat each restricted portion will be 250 voits. If, on the other hand,five restricted portions are used in the link` the voltage at eachrestricted portion will be decreased to 100 volts, and the number ofseparate pieces resulting from the blowing of the fuse will, of course.in each case be one less than the number of restricted portions. Thus,in a link with two restricted portiogs a single piece will be separatedfrom theV link; with three restricted portions two pieces will beseparated, and so on.

I am aware that fuse links for use in the open air have been heretoforemade with a plurality of restricted portions, but I have found that theoperation of such links is entirely different from the operation of myim proved inclosed fuses, inasmuch as practical tests have demonstratedthat under shortcircuit conditions links of the former type arecompletely melted or volatilized and sustain an arc for a` considerableperiod, while under the same conditions my improved inclosed fuses openthe circuit instantly and the metal between the restricted portions ofthe links is separated without appreciable melting from the rest of thelink.

Although in the present specification I have described the link ci myinclosed fuse as having a plurality of restricted or more readilymelting portions and as being used ployed with hlling material.

A further object'of my invention consists inthe use of a dat fusiblelink orl only slightly less width than the interior diameter ot thecylindrical fuse casing. By thus using a link of relatively great width,and by increasing this width and the interior diameter of the casing asthe capacity of the fuse is increased, means are provided for preventingthe use in a fuse casing of a fuse link which 4is 'ot greater capacitythan that for which the fuse is rated.

These and other objects of my invention will be more readily understoodby reference to the accompanying drawings, in which- Figure 1 is alongitudinal section through my improvedtuse;

Fig. 2 is a longitudinal the line 2-2 ot Fig. 1;

Fig. 3 is a transverse line 3-3 ot Fig. 1;

Fig. t isa perspective of the uselink section taken on the used in myimproved fuse; and

Fig. 5 is an enlarged fragmentary longitudinal section of the end ot thefuse casingyshowing a portion of the cap applied thereto. A

The cylindrical fuse casing 10 is preterably of fiber or other suitablenon-conducting material, and is provided at its ends with the threads11. The terminals 12 eX- tend into the ends ot the casing 10, and arealined and centered in position by means of tia the washers 13, whichare preferably ot1 the same type as ydescribed in Letters Fatent No.1,092,498'is'sued to Edward B. Mallory, assignor to lEconomy Fuse &Manufacturing (Company, on April 7 1914. Outside of the washers 13at'each end of the fuse casing is placed another washer 14:, preferablyot resilient material, such as leather, rubber, or the like. The washers14 are provided with apertures ot' ysubstantially the same size as theinner ends ot the terminals 12. Just outside of each of the washers 11111 preferably employ a metallic washer 15, which is identical in shapewith the washers 1li, and is provided with asimilar aperture 16 otsubstantially the same size'as the inner portion of the terminal 12. linassembling the fuse, the washer 15 is rst placed in pos1- tion byslipping over the inner end oi-a the 'terminal'.12 until it is broughtinto engagement with the shottlder'17 on vsaid terminal. The leatherwasher 1t is next placed in positionin the same manner, and the washers13 are then placed on the terminal by passing their tongues through theaperture18 in the terminal in the manner described in the Mallory patentabove mentioned.

Flach oit the terminals 12 and its assosection taken on narrate ciatedwashers, which have just been descrlbed, 1s held in position by means ofthe end cap. 19, which has an interiorly threaded skirt engaging thethreads 11 on the end of the casing 10. Each end cap 19 is provided withan inwardly extending flange 20, which engages the washer 15 so that onscrewing home the cap 19 the inner washer 13 is brought firmly incontact with the end of the casing 10, while at the same time the washer14C is pressed firmly against the outer washer 13 and against theterminal 12. At the same time the flange 20 of the cap 19 has a lirmengagement with the washer 15, thus edectually closing the end of thecasing 10. A restricted path of escape for the gases which arevgenerated on blowing of the -`fuse is formed by the clearance betweenthe threads 11 of the casing 10, and the interior threads on the skirtof each end cap 19. This clearance is clearly represented in Fig. 5 bythe spaces 21.

The link which is used in my improved fuse is preferably flat, and ispreferably of a readily fusible metal, such as zinc. This link,represented in the drawings by 22, is fastened to the inner ends of theterminals 12 by coperative action of the screws 23 and the nuts 24. Thelink 22 is provided near its ends with the notches 25, thus forming therestricted portions 26 of substantially reduced cross-sectional area andan intermediate portion 27 of substantially greater current-carryingcapacity than said restricted portions. This intermediate portion 27 ofthe link is only slightly narrower than the interior diameter of thecylindrical casing 10, and is correspondingly thin in order to give therequisite cross-sectional area of metal for any given capacity of fuse.By making fuses of dierent capacities of correspondingly diderentwidths, it becomes impossible to insert in a given tuse casing a link ofgreater capacity than that for which the fuse was designed.

1t will be revident from the above descrip tion that on blowing of thefuse the link 22 will melt at the intermediate portion 27 of the linkwill drop out of or become separated from the latter withoutvolatilization of the metal of said intermediate portion. The `gaseswhich its restrictedy portions 26 and prior open link fuses having aplurality of restricted portions.

After blowing of the fuse the' terminals 12 are readily removed by irstremoving the caps 19, a new link is fastened to the inner ends of theterminals, and the fuse is then again assembled, as indicated in Figs. 1and Q.

It will be apparent to those skilled in the art that'many changes couldbemade in the detailed construction of the various parts which I havedescribed without departing from the spirit or scope of my invention.

-lVhat I claim is:

1. In an inclosed fuse, the combination of an inclosing casing,terminals carriedby said casing,land a fusible link extending throughsaid casing and between said terminals, said link being provided alongits length with a plurality of portions of substantially lesscurrent-carrying capacity than that of an intermediate portion betweensaid first-mentioned portions, whereby on the blowing of said fuse saidlink will melt at said portions of less current-carrying capacity andsaid intermediate portion will be separated from the rest of the linkwithout melting said intermediate portion.

2. In an inclosed fuse, the combination of an inclosing casing, theinterior of which has' restricted communication with the outeratmosphere, a pair of terminals carried by said casing, and a fusiblelink extending through said casing and between said terminals, said linkbeing provided along its length with an intermediate portion ofsubstantially greater carrying capacity than that of the portions ofsaid link at the ends of said intermediate portion, whereby on blowingof said -fuse said link will melt at the portions located at the ends ofsaid intermediate portion and said intermediate portion will beseparated from the rest of the link without melting said intermediateportion.

3. In an inclosed fuse, the combination of a casing, a pair of terminalscarried by said casing, and a fusible link extending through said casingand having its ends electrically connected with said terminals, saidlink having along its length a plurality of restricted portions ofsubstantially less crosssectional area than that of an intermediateportion of said link between said restricted portions, whereby onblowing of said fuse said link will melt at said restricted portions andthe intermediate portion of said link will be separated from the rest ofthe link Without melting said intermediate portion. l

l. In a cartridge fuse, the combination of a casing, terminals at theends of said casing, and a flat fusible link extending through saidcasing and having its ends electrically connected with said terminals,said link being provided along its length with an intermediate portionof substantially greater cross-sectional area than the portions of saidlink at the ends of said intermediate portion, whereby on blowing saidfuse said link will melt at the portions located at the ends of saidintermediate portion and said intermediate portion will be separatedfrom the rest of said link without melting said intermediate portion; c

5. In a cartridge fuse, the combination of a cylindrical casing,terminals at the ends of said casing, and a fiat fusible link extendingthrough said casing and between said terminals, said link having alongits length a pair of portions of substantially less current-carryingcapacity than that of an intermediate portion between saidfirst-mentioned portions, said intermediate portion being of a widthonly slightly less than the interior diameter of said casing.

6. In a cartridge fuse, 'the combination of a cylindrical casing,terminals carried by the ends of said casing, and a flat zinc linkextending through said casing and lbetween said terminals, said linkhaving along its length a plurality of portions of substantially lesscross-sectional area than that of an intermediate portion between saidfirstmentioned portions.

In witness whereof, I hereunto subscribe my name this 16th day of June,A. D. 1914.

ALFRED L. EUSTICE.

Witnesses:

HENRY M. HUXLEY, f .H. C. JACOBS.

